Back to EveryPatent.com
| United States Patent |
5,158,666
|
|
Reid
|
October 27, 1992
|
Use of 1-(2-aminoethyl) piperazine to inhibit heat exchange fouling
during the processing of hydrocarbons
Abstract
The present invention is directed to an antioxidant material and its use in
petroleum and petrochemical processes to reduce and/or control fouling
problems specifically as regards hydrocarbons having a bromine number of
10 or less and containing oxygen. The inventive antioxidant material is
1-(2-aminoethyl) piperazine.
| Inventors:
|
Reid; Dwight K. (Houston, TX)
|
| Assignee:
|
Betz Laboratories, Inc. (Trevose, PA)
|
| Appl. No.:
|
566648 |
| Filed:
|
August 13, 1990 |
| Current U.S. Class: |
208/48AA; 44/335; 585/2 |
| Intern'l Class: |
G10G 009/16 |
| Field of Search: |
208/48 AA
585/2
44/335
|
References Cited
U.S. Patent Documents
| 2329251 | Sep., 1943 | Chenicek | 44/66.
|
| 3218322 | Nov., 1965 | Orloff | 585/5.
|
| 3558470 | Jan., 1971 | Gillespie | 208/48.
|
| 4200518 | Apr., 1980 | Mulvany | 208/48.
|
| 4319063 | Mar., 1982 | Droracek et al. | 208/48.
|
| 4390412 | Jun., 1983 | Droracek et al. | 208/48.
|
| 4431514 | Feb., 1984 | Ferm | 208/48.
|
| 4647290 | Mar., 1987 | Reid | 44/57.
|
| 4714793 | Dec., 1987 | van Eijl | 585/2.
|
| 4744881 | May., 1988 | Reid | 208/48.
|
| 4749468 | Jun., 1988 | Roling et al. | 208/48.
|
| 4810354 | Mar., 1989 | Roling et al. | 208/48.
|
| 4867754 | Sep., 1989 | Reid | 44/72.
|
Other References
Standard Methods for Analysis and Testing of Petroleum and Related
Products, vol. 1, 1988 pp. 130.15-130.16.
|
Primary Examiner: Morris; Theodore
Assistant Examiner: Diemler; William C.
Attorney, Agent or Firm: Ricci; Alexander D., Von Neida; Philip H.
Claims
What I claim is:
1. A method of inhibiting fouling of heat transfer surfaces during the
processing of a hydrocarbon in contact with said heat transfer surfaces,
said hydrocarbon having a bromine number of 10 or less and containing
unsaturated or olefinic components which are induced by the presence of
oxygen to react to form fouling materials, which consists essentially of
adding to said hydrocarbon being processed a sufficient amount, for the
purpose of inhibiting fouling, of 1-(2-aminoethyl) piperazine (AEP).
2. A method according to claim AEP is added to said hydrocarbon in an
amount of from 1 to 10,000 ppm of the petroleum or hydrocarbon
petrochemical being processed.
3. A method according to claim 2 wherein the AEP is added to said
hydrocarbon in an amount of from 15 to 200 ppm of the petroleum or
hydrocarbon petrochemical being processed.
4. A method according to claim 1 wherein said heat transfer surfaces are
heat exchangers.
5. A method according to claim 1 wherein the AEP is in an organic solvent.
Description
FIELD OF THE INVENTION
This invention relates to a process for inhibiting and preventing fouling
in refinery and petrochemical feedstocks during processing. More
particularly, this invention relates to hydrocarbon fuel fouling,
manifested by color degradation, particulate formation and gum generation
in hydrocarbon fuel oils undergoing petroleum processing.
BACKGROUND OF THE INVENTION
Fouling can be defined as the accumulation of unwanted matter on heat
transfer surfaces. This deposition can be very costly in refinery and
petrochemical plants since it increases fuel usage, results in interrupted
operations and production losses and increases maintenance costs.
Deposits are found in a variety of equipment preheat exchangers, overhead
condensers, furnaces, heat exchangers, fractionating towers, reboilers,
compressors and reactor beds. These deposits are complex but they can be
broadly characterized as organic and inorganic. They consist of metal
oxides and sulfides, soluble organic metals, organic polymers, coke, salt
and various other particulate matter. Chemical antifoulants have been
developed that effectively combat fouling.
The chemical composition of organic foulants is rarely identified
completely. Organic fouling is caused by insoluble polymers which
sometimes are degraded to coke. The polymers are usually formed by
reactions of unsaturated hydrocarbons, although any hydrocarbon can
polymerize. Generally, olefins tend to polymerize more readily than
aromatics, which in turn polymerize more readily than paraffins. Trace
organic materials containing hetero atoms such as nitrogen, oxygen and
sulfur also contribute to polymerization.
Polymers are generally formed by free radical chain reactions. These
reactions, shown below, consist of two phases, an initiation phase and a
propagation phase. In Reaction 1, the chain initiation reaction, a free
radical represented by R., is formed (the symbol R. can be any
hydrocarbon). These free radicals, which have an odd electron, act as
chain carriers. During chain propagation, additional free radicals are
formed and the hydrocarbon molecules (R) grow larger and larger (see
Reaction 4), forming the unwanted polymers which accumulate on heat
transfer surfaces.
Chain reactions can be triggered in several ways. In Reaction 1, heat
starts the chain. Example: When a reactive molecule such as an olefin or a
diolefin is heated, a free radical is produced. Another way a chain
reaction starts is shown in Reaction 3. Metal ions initiate free radical
formation here. Accelerating polymerization by oxygen and metals can be
seen by reviewing Reactions 2 and 3.
As polymers form, more polymers begin to adhere to the heat transfer
surfaces. This adherence results in dehydrogenation of the hydrocarbon and
eventually the polymer is converted to coke.
1. Chain Initiation
R--H - - - R.+H.
2. Chain Propagation
a. R.+O.sub.2 - - - R--O--O.
b. R--O--O.+R'--H - - - R.+R--O--O--H
3. Chain Initiation
a. Me.sup.++ +RH - - - Me.sup.+ R.+H.sup.+
b. Me.sup.++ +R--O--O--H - - - Me.sup.+ R--O--O.+H.sup.+
4. Chain Termination
a. R.+R. - - - R--R'
b. R.+R--O--O. - - - R--O--O--R
In refineries, deposits usually contain both organic and inorganic
compounds. This makes the identification of the exact cause of fouling
extremely difficult. Even if it were possible to precisely identify every
single deposit constituent, this would not guarantee uncovering the cause
of the problem. Assumptions are often erroneously made that if a deposit
is predominantly a certain compound, then that compound is the cause of
the fouling. In reality, oftentimes a minor constituent in the deposit
could be acting as a binder, a catalyst, or in some other role that
influences actual deposit formation.
The final form of the deposit as viewed by analytical chemists may not
always indicate its origin or cause. Before openings, equipment is
steamed, waterwashed, or otherwise readied for inspection. During this
preparation, fouling matter can be changed both physically and chemically.
For example, water-soluble salts can be washed away or certain deposit
constituents oxidized to another form.
In petrochemical plants, fouling matter is often organic in nature. Fouling
can be severe when monomers convert to polymers before they leave the
plant. This is most likely to happen in streams high in ethylene,
propylene, butadiene, styrene and other unsaturates. Probable locations
for such reactions include units where the unsaturates are being handled
or purified, or in streams which contain these reactive materials only as
contaminants.
Even through some petrochemical fouling problems seem similar, subtle
differences in feedstock, processing schemes, processing equipment and
type of contaminants can lead to variations in fouling severity. For
example, ethylene plant depropanizer reboilers experience fouling that
appears to be primarily polybutadiene in nature. The severity of the
problem varies significantly from plant to plant, however. The average
reboiler run length may vary from one to two weeks up to four to six
months (without chemical treatment).
Although it is usually impractical to identify the fouling problem by
analytical techniques alone, this information combined with knowledge of
the process, processing conditions and the factors known to contribute to
fouling, are all essential to understanding the problem.
There are many ways to reduce fouling both mechanically and chemically.
Chemical additives often offer an effective anti-fouling means; however,
processing changes, mechanical modifications equipment and other methods
available to the plant should not be overlooked.
Antifoulant chemicals are formulated from several materials: some prevent
foulants from forming, others prevent foulants from depositing on heat
transfer equipment. Materials that prevent deposit formation include
antioxidants, metal coordinators and corrosion inhibitors. Compounds that
prevent deposition are surfactants which act as detergents or dispersants.
Different combinations of these properties are blended together to
maximize results for each different application. These "polyfunctional"
antifoulants are generally more versatile and effective since they can be
designed to combat various types of fouling that can be present in any
given system.
Research indicates that even very small amounts of oxygen can cause or
accelerate polymerization. Accordingly, anti-oxidant-type antifoulants
have been developed to prevent oxygen from initiating polymerization.
Antioxidants act as chain-stoppers by forming inert molecules with the
oxidized free radical hydrocarbons, in accordance with the following
reaction:
Chain Termination
ROO.Antioxidant - - - ROOH +Antioxidant (H)
Surface modifiers or detergents change metal surface characteristics to
prevent foulants from depositing. Dispersants or stabilizers prevent
insoluble polymers, coke and other particulate matter from agglomerating
into large particles which can settle out of the process stream and adhere
to the metal surfaces of process equipment. They also modify the particle
surface so that polymerization cannot readily take place.
Antifoulants are designed to prevent equipment surfaces from fouling. They
are not designed to clean up existing foulants. Therefore, an antifoulant
should be started immediately after equipment is cleaned. It is usually
advantageous to pretreat the system at double the recommended dosage for
two or three weeks to reduce the initial high rate of fouling immediately
after startup.
The increased profit possible with the use of antifoulants varies from
application to application. It can include an increase in production, fuel
savings, maintenance savings and other savings from greater operating
efficiency.
There are many areas in the hydrocarbon processing industry where
antifoulants have been used extensively; the main areas of treatment are
discussed below.
In a refinery, the crude unit has been the focus of attention because of
increased fuel costs. Antifoulants have been successfully applied at the
exchangers; downstream and upstream of the desalter, on the product side
of the preheat train, on both sides of the desalter makeup water exchanger
and at the sour water stripper.
Hydrodesulfurization units of all types experience preheat fouling
problems. Among those that have been successfully treated are reformer
pretreaters processing both straight run and coker naphtha, desulfurizers
processing catalytically cracked and coker gas oil, and distillate
hydro-treaters. In one case, fouling of a Unifiner stripper column was
solved by applying a corrosion inhibitor upstream of the problem source.
Unsaturated and saturated gas plants (refinery vapor recovery units)
experience fouling in the various fractionation columns, reboilers and
compressors. In some cases, a corrosion control program combined with an
antifoulant program gave the best results. In other cases, an application
of antifoulants alone was enough to solve the problem.
Cat cracker preheat exchanger fouling, both at the vacuum column and at the
cat cracker itself, has also been corrected by the use of antifoulants.
The two most prevalent areas for fouling problems in petrochemical plants
are at the ethylene and styrene plants. In an ethylene plant, the furnace
gas compressors, the various fractionating columns and reboilers are
subject to fouling. Polyfunctional antifoulants, for the most part, have
provided good results in these areas. Fouling can also be a problem at the
butadiene extraction area. Both antioxidants and polyfunctional
antifoulants have been used with good results.
In the different design butadiene plants, absorption oil fouling and
distillation column and reboiler fouling have been corrected with various
types of antifoulants.
Chlorinated hydrocarbon plants, such as VCM, EDC and perchloroethane and
tri-chloroethane have all experienced various types of fouling problems.
The metal coordinating/antioxidant-type antifoulants give excellent
service in these areas.
SUMMARY OF THE INVENTION
This invention relates to processes for inhibiting the degradation,
particulate and gum formation in hydrocarbons prior to or during
processing which comprises adding to the hydrocarbons an effective
inhibiting amount of an antioxidant, 1-(2-aminoethyl) piperazine (AEP).
More particularly, this invention relates to inhibiting the degradation,
particulate and gum formation in hydrocarbons that have a bromine number
of 10 or less prior to or during processing at elevated temperatures.
Accordingly, it is an object of the present invention to provide processes
for inhibiting the degradation, particulate and gum formation in
hydrocarbon fuels prior to or during processing.
It is a further object of the present invention to inhibit fouling in
petroleum and hydrocarbon petrochemicals during processing.
It is still a further object of the present invention to inhibit fouling in
hydrocarbons having a bromine number of 10 or less.
It is still another object of the present invention to inhibit fouling in
hydrocarbons through the use of a single chemical.
These and other objects and advantages of the present invention will be
apparent to those skilled in the art upon reference to the following
description of the preferred embodiments.
THE PRIOR ART
U.S. Pat. No. 4,744,881 (Reid) teaches the use of a composition of an
unhindered or hindered phenol and a strongly basic amine compound to
control fouling in hydrocarbon fluids having a bromine number greater than
10. This patent discloses N-(2-aminoethyl) piperazine as one of the amines
that can be utilized in the process.
U.S. Pat. No. 2,329,251 (Chenicek) teaches an early method of inhibiting
gum formation in hydrocarbon distillates using an alkylene polyamine salt
of an organic acid.
U.S. Pat. No. 4,647,290 (Reid) teaches the use of a composition of
N-(2-aminoethyl) piperazine and N,N-diethylhydroxylamine to inhibit color
deterioration of distillate fuel oils. The combination of these two
chemicals provide a more effective color stabilized composition than when
either is used alone.
U.S. Pat. No. 4,867,754 (Reid) teaches the use of a composition of a
phosphite compound and an organic compound containing a tertiary amine of
the formula T.sub.3 N to stabilize distillate fuel oils. 2-(aminoethyl)
piperazine is disclosed as one of the possible amines used. This
combination provides a higher degree of stabilizaion of distillate fuel
oils than when the individual species are used alone.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to the inhibition of fouling of heat transfer
surfaces during the processing of a hydrocarbon having a bromine number of
10 or less. The hydrocarbon contains substituents which are induced by
oxygen to react to form fouling materials in contact with the heat
transfer surfaces. This method consists essentially of adding to the
petroleum or hydrocarbon system being processed a sufficient amount for
the purpose of 1-(2-aminoethyl) piperazine (AEP).
The use of aminoethyl piperazine (AEP) is known in the petroleum refining
industry as an antioxidant in hydrocarbon processing. U.S. Pat. No.
4,744,881 (Reid) which is wholly incorporated by reference herein teaches
the use of a composition of an unhindered or hindered phenol and a
strongly basic amine compound to control fouling in high temperatures
hydrocarbon fluids having a bromine number greater than ten. U.S. Pat. No.
4,647,290 (Reid) which is wholly incorporated by reference herein teaches
the use of a composition of N-(2-aminoethyl) piperazine and
N,N-diethylhydroxylamine to inhibit color deterioration of distillate fuel
oils.
Reid ('881) teaches the use of a synergistic composition of a phenol and an
amine to control fouling in hydrocarbon fluids having bromine numbers in
excess of 10. At column 6, line 13 of Reid ('881), test results indicate
that AEP is a poor antioxidant in higher bromine number hydrocarbon fluids
when used alone. There is nothing in the specification nor the test
results in Reid ('881) that would suggest that AEP, acting alone, would be
a good antioxidant in hydrocarbon fluids having bromine numbers less than
10.
Reid ('290) is directed towards color inhibition in distillation fuel oils
through the synergistic combination of N-(2-aminoethyl) piperazine and
N,N-diethylhydroxyolamine. Reid ('290) teaches in Col. 5, lines 41-45 and
Col. 6, lines 1-2 that neither of these two chemical species, when used
alone, are effective antioxidants in the hydrocarbon systems taught in
Reid ('290). This patent is also directed towards finished products that
are in transit or storage and their protection from color contamination.
The present invention is directed to hydrocarbons that are undergoing
petroleum refining.
Surprisingly, the present inventor has discovered that 1-(2-aminoethyl)
piperazine is effective as an antifoulant in hydrocarbons having a bromine
number of 10 or less. This is defined as the number of centigrams of
bromine which are reacted with 1 gram of hydrocarbon under certain
conditions. As compared with the prior art, this antioxidant works well as
an antifoulant in hydrocarbons without the use of other chemicals.
The treatment range for AEP clearly is dependent upon the severity of the
fouling problem due to free radical polymerization encountered as well as
the activity of the AEP utilized. For this reason, the success of the
treatment is totally dependent upon the use of a sufficient amount of the
AEP. Broadly speaking, the treatment recommendations could be in the range
of 1 to 10,000 parts per million (ppm) of petroleum or petrochemical being
processed with perhaps 15 to 200 ppm being applicable in most cases. The
AEP can be added to the hydrocarbon either as a concentration or as a
solution using a suitable carrier solvent which is compatible with the AEP
and the hydrocarbon.
The hydrocarbons where the present invention is effective are those which
contain unsaturated or olefinic components which components are induced by
the presence of oxygen to polymerize or react. As a general rule, any
hydrocarbon media having a bromine number of 10 or less would be such
where fouling due to oxygen induced reactions would be a problem. These
hydrocarbons, where such is the case, include the middle distillate
feedstocks such as light cycle oils and cyclo-paraffins that have a
bromine number of 10 or less.
In order to more clearly illustrate this invention, the data set forth
below was developed. The following examples are included as being
illustrations of the invention and should not be construed as limiting the
scope thereof.
EXAMPLES
Tests were conducted to study the effect of various additives and AEP on
the amount of gum formed in various distillate products in a three hour
reflux test. The results appear in Tables I-IV below.
The test procedure employed was a modified version of ASTM 381. A 50 ml
refluxed fuel sample in a 100 ml beaker was concentrated in a gum bath
(temperature 240.degree. C.) through Jet evaporation to 20 ml and allowed
to cool for 30 minutes. The 20 ml sample was transferred to a 120 ml
centrifuge tube containing 80 ml of heptane and centrifuged for 8 to 10
minutes. The 100 ml mixture was filtered through a 0.8 micron glass fiber
filter. The residual material in the beaker was weighed and this value
recorded. The precipitate on the filter was weighed and recorded. The sum
of both multiplied by two is taken to be total gum solids in mg/100 ml.
TABLE 1
______________________________________
DHT Tops
HDS Feedstock (West Coast) Refinery
Additives used at 1000 ppm active
Bromine Number = 7.3
Total Washed Gums
Treatment (mg/100 ml)
______________________________________
Control (Avg. 5) 45.0
Diethylethanolamine
75.0
1-(2-aminoethyl) piperazine
8.0
______________________________________
TABLE II
______________________________________
Catalytic Crack Light Gas Oil
Midwestern Refinery Feedstock
Additives used at 750 ppm active
Bromine Number = 7.0
Total Washed Gums
Treatment (mg/100 ml)
______________________________________
Control 99.0
DEHA 142.0
ACS-1246 148.0
Inhibitor B 110.0
1-(2-aminoethyl) piperazine
38.0
______________________________________
TABLE III
______________________________________
Heavy Gas Oil
West Coast Refinery
Additives used at 750 ppm active
Bromine Number = 1
Total Washed Gums
Treatment (mg/100 ml)
______________________________________
Control (Avg. 4) 156.0
1-(2-aminoethyl) piperazine
95.0
______________________________________
TABLE IV
______________________________________
Virgin Light Gas Oil Feedstock
West Coast Refinery
Additives used at 750 ppm active
Bromine Number = 1
Total Washed Gums
Treatment (mg/100 ml)
______________________________________
Control 407
Inhibitor A 418
1-(2-aminoethyl) piperazine
172
______________________________________
Inhibitor A is a commercial substituted pphenylene diamine/phosphite
antioxidant
The results in Tables I-IV indicate the substantially better performance of
AEP in inhibiting gum formation compared with other commercial
antifoulants. The less gums that are accumulated in the wash, the more
efficacious the treatment agent.
While this invention has been described with respect to particular
embodiments thereof, it is apparent that numerous other forms and
modifications of this invention will be obvious to those skilled in the
art.
Top